Grinding wheel dressing device for shaped wheels

ABSTRACT

A grinding wheel dressing device for gear cutter grinding wheels, especially for helically fluted gear cutters, the dressing device having a mechanism for the generation of an infinite number of convexly corrected wheel taper dressing paths from two independently adjustable eccentric cranks: One crank produces a primary motion component, the other produces a transverse, secondary motion component which is adjustable to zero and shiftable for correction of curvature skew.

United States Patent Lorenz Oct. 28, 1975 v [5 GRINDING WHEEL DRESSING DEVICE 2,904,029 9/1959 Hoglund 125/11 TP FOR SHAPED WHEELS 75 1 FOREIGN PATENTS OR APPLICATIONS 1 Inventor glam-ed coburg'creldmz 1,198,622 7/1970 United Kingdom 125/11 cc ermany [73] sigma a: Primary ExaminerHarold D. Whitehead er zeugmaschmenfabnk Coburg Attorney, Agent, or FirmJoseph A. Geiger Germany [22] Filed: Jan. 29, 1974 [57] ABSTRACT [21] App]. No.: 437,709

A grinding wheel dressing device for gear cutter grinding wheels, especially for helically fluted gear cutters, [3O] Fore'gn Apphcatlon Pnonty Data the dressing device having a mechanism for the gener- Feb. 10, 1973 Germany ..'2306695 ation of an infinite number of convexly corrected wheel taper dressing paths from two independently ad- [52] U.S. Cl 125/11 CC j tabl ent i ranks; One crank produces a pri- II-lt. CLZ nary motion component the other produces a trans- Field 0f Search 11 11 TP verse, secondary motion component which is adjustable to zero and shiftable for correction of curvature [56] References Cited skew.

UNITED STATES PATENTS 2 I 2,326,073 8/1943 Seyferth 125/11 cc 12 Chums l f' F'gure US. Patent Oct. 28, 1975 BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to devices for the dressing of shaped grinding wheels, and in particular to devices for the dressing of wheels for grinding the tooth faces of milling cutters such as gear cutters, with a dressing head moving along a two-dimensional displacement path generated by motion components which are perpendicular to one another.

2. Description of the Prior Art Cutters for the milling of envolute gear teeth usually have radially relieved cutting teeth. In order to preserve the true tooth profile after repeated regrinding of the tooth faces, it is necessary that the tooth face is oriented along a straight line in the planar cross section of the cutter, the extension of the line passing through the cutter axis in the case of a zero-degree rake angle. For gear cutters having straight flutes between their teeth, the straight-line tooth face is obtained by means of flattapered disc grinding wheels whose straight-line tapered contour is obtained by means of a straight-line displacement of the dressing head of a wheel dressing device. When helically fluted gear cutters are ground with such a straighttapered grinding wheel, the resultant tooth faces have a convex tooth face outline in the planar cross section, the theoretical straight line of the tooth face being a tangent thereto. This undesirable convexity decreases as the grinding wheel diameter decreases and as the angle between the grinding wheel faces increases.

The above-mentioned deviation from the theoretical tooth face line in the case of helically fluted gear cutters can be compensated for by making an appropriate convex contour correction on the normally straightline contour of the grinding wheel. The exact outline of such a corrected grinding wheel contour, in geometric terms, corresponds to a mathematically solvable curve equation of higher order, the equation parameters being a function of various geometric dimensions of the cutter and of the grinding wheel, especially as far as the diameter and the angle of taper of the latter are concerned. Thus, a certain number of different gear cutters and different grinding wheels require a correspondingly multiplied number of corrected contour curves to which the theoretical straight line is in each case a tangent.

In the past, these corrected contour curves of shaped grinding wheels for the grinding of helically fluted gear cutter faces had to be obtained by means of known j grinding wheel dressing devices using single or multiple plates is extremely difficult and costly. Lastly, the' known grinding wheel dressing devices which are adapted to operate with dressing templates, if they are to be used for a wide range of dimensions, are very complex in construction and therefore expensive.

SUMMARY OF THE INVENTION It is a primary objective of the present invention to provide a device for the dressing of shaped grinding wheels for envolute gear cutters, especially of the helically fluted type, where the earlier-mentioned shortcomings are eliminated by means of simple expedients, and which device requires a minimum of space by permitting an adjustment of the dressing head path in such a way that the end points of the dressing head path coincide with the theoretically calculated convexity, that the theoretical straight line of the wheel contour is a tangent thereto, and that the remaining curvature of the calculated convexity is approached with minimal error. v

In order to attain the above objective, the invention suggests a mechanism for the generation of the dressing head path by means of two adjustable eccentric drive cranks arranged on a common drive shaft. This drive shaft is preferably rotated by means of a rack and pinion drive, and the motions of the eccentric cranks are transmitted via mechanical linkages to an arm which carries the dressing'head.

According to a further characteristic of the invention, one of the transmitting mechanisms includes a cylindrical plunger and a straight-line guide therefor, the plunger motion being directly transmitted to the dressing head arm, while the other transmitting mechanism includes a guided cylindrical plunger driving a shaft which carries an angularly adjustable eccentric from which a second motion component is transmitted to the dressing head arm via a forked lever as a rocking motion of that lever.

A primary advantage of the invention derives from the possibility of producing an infinite number of curved displacement paths for the dressing head, with displacement path end points which coincide with the calculated curvatures and whose mid-portions exhibit a minimal deviation from the theoretical curvature, while the outline of a grinding wheel dressed along the theoretical straight line represents a tangent to this curvature. This convenient adjustability of the dressing curvature makes it possible to adjust the dressing device for optimal combinations of grinding wheel diameters and angles of taper, thereby reducing the error of curvature to an absolute minimum. The generation of the curved displacement path of the dressing head from two motion components which are perpendicular to one another allows for the independent adjustment of each motion component on a separate eccentric drive crank. Besides its convenience of operation, the novel device of the invention offers the advantage of simplicity of structure, which is reflected in a correspondingly lowered cost of manufacture.

In a preferred embodiment of the invention each of two eccentric drive cranks includes a radially adjustable crank arm carrying a follower pin engaging a slot of a guided plunger, the plungers in turn moving the dressing head arm.

Another preferred feature of the invention suggests that the plunger which transmits the longitudinal displacement component of the dressing head path is guided for movement along its axis and for rotation thereabout and that it is rigidly connected to the dressing head arm, while the plunger transmitting the second motion component is only longitudinally movable along its axis and carries rack teeth engaging a pinion a secondary shaft which is attached to an eccentric )se rotational motion is transmitted to the dressing d arm via a forked lever. The latter is rigidly conted to the first plunger and dressing head arm. The ion on the secondary shaft is angularly adjustable in [tion to the eccentric. This arrangement makes it sible to obtain infinitely variable angular adjustnts of the position and displacement angle of the ecitric so that both the height of path curvature and its :w can be adjusted at random for the closest possible 'respondence with the theoretical curvature. .astly, provision is made that the various adjustment ues on the transmission mechanisms can be ascerned visually by means of pointers and dials. For in- .nce, the head carrier assembly may carry a movable inter radially extending from the axis of the plunger iich indicates the distance of primary longitudinal m displacement. Similarly, the pinion on the secondy shaft may be connected to a dial drum facing a stamary pointer which indicates the total angular disacement of the secondary shaft, while a second dial I the drum cooperating with a pointer on the secondy shaft indicates the relative angular position be- Ieen the pinion and the eccentric on the secondary .hft. The latter is adjustable relative to the drum and ,nion by means of a clamping connection.

BRIEF DESCRIPTION OF THE DRAWING Further special features and advantages of the invenon will become apparent from the description follow- 1g below, when taken together with the accompanying rawing which illustrates, by way of example, an emodiment of the invention represented as follows:

The FIGURE of the drawing shows in a schematic lerspective representation a motion generating mechalism for a grinding wheel dressing device embodying he invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The working face of a tapered grinding wheel 1 is dressed by means of a dressing head 2 carrying a diamond dressing point, for example. The dressing head 2 is arranged at the far end of a horizontal arm 3a, and the latter is rigidly connected with a vertical lever 3. The lever 3 and arm 3a are pivotable around a pivot axis 4 and movable longitudinally along the same axis in a manner which will be described further below.

The dressing head 2 is displaced along a twodimensional path along the grinding wheel contour. Both the primary longitudinal motion component X, which is parallel to the theoretical straight line of the wheel taper, and the secondary transverse motion component Y, obtained through a rocking motion of the lever 3, are derived from a rack 5 which is suitably guided for horizontally reciprocating motion. The rack 5 cooperates with a pinion 6 mounted on a vertical shaft 7. The latter carries two eccentric drive cranks 8 and 9, the upper crank 8 producing the secondary motion component (Y) and the lower crank 9 producing the primary motion component (X).

In the embodiment illustrated in the drawing, the eccentric drive cranks 8 and 9 have hubs- 8a and 9a clampingly holding radially adjustable cranks 8b and 9b to the far ends of which are attached follower pins 80 and 90, respectively. These followers 80 and 9c engage guide grooves 10a and 11a of the guided plungers 10 and 11. The lower horizontal plunger 11, which cooperates with the lower crank 9, has its axis at 4 and is guided for longitudinal motion and rotation with respect to that axis, while the upper horizontal plunger 10, which cooperates with the upper crank 8, is arranged perpendicular to the axis 4 and at a vertical distance therefrom, thereby providing the necessary leverage for the rocking motion of the lever 3.

The longitudinal displacement of the lower plunger 1 1 dervied from the eccentric crank 9 is transmitted directly to the rod 3 and dressing head arm 3a by means of an intermediate rod 12 which provides a rigid connection between the plunger 11, the lever 3 and the dressing head arm 3a. The longitudinal extent of the head displacement path in the primary direction X is adjustable through adjustment of the eccentricity of the follower pin 9c on the crank arm 9b, the resulting displacement distance being visually ascertainable from a horizontal dial l4 and a pointer 13 which is attached to the head carrier assembly constituted by plunger 11, rod 12, lever 3, and head arm 3a, which are rigidly connected to one another.

The follower pin 8c on the crank arm 8b of the upper drive crank 8 is radially adjustable between a given maximum eccentricity and zero eccentricity (shown in the FIGURE), in which latter case the upper plunger 10, connected to the drive crank 8 via a transverse groove 10a receiving its follower pin 8c, remains m0- tionless during the rotation of shaft 7 so that the resulting displacement path of the dressing head 2 is a straight line. An adjusted eccentricity on the eccentric drive crank 8 causes the plunger 10 to execute a longitudinal motion which is transmitted to the lever 3 of the head carrier assembly by means of a cooperating pinion 15 on the horizontal secondary shaft 17 whose rotary motion is transmitted to an elongated eccentric 16 engaging the fork 3b on the upper end of lever 3 in an axially indeterminate connection. Thus, for a given eccentricity of the follower pin 8c and a given reciprocating angle a on the drive shaft 7, the plunger 10 will produce an angular displacement B on the secondary shaft 17, which in turn will cause a rocking motion of angle 7 on the lever 3 around the axis 4. This rocking displacement y directly determines the secondary motion component Y of the dressing head displacement path.

The eccentric 16 is solidary with the secondary shaft 17, but the pinion l5, likewise mounted on this shaft, is clamped thereto so as to give it an infinite angular adjustability. For this purpose, the pinion 15 has a tubular extension 15a connecting it to a dial drum 15b at the opposite side of which is positioned a flange 19 which is solidary with the secondary shaft 17. A clamping screw 18 adjustably holds the dial drum 15b against the flange 19. A stationary pointer 20 cooperates with a dial 21 on the dial drum 15b to visually indicate the dis- B of the pinion 15 which, as mentioned earlier, is determined by the eccentricity of crank arm 8b. A second dial 22 on the dial drum 15b cooperates with a pointer 19a on the flange 19 to indicate the angular adjustment position of the eccentric 16 in relation to the pinion 15.

Longitudinal reciprocation of the rack 5 produces a rotational displacement of the pinion 6, shaft 7, and eccentric cranks 8 and 9 connected thereto, of an angle a which is preferably This rotary motion is converted into a longitudinal motion of the guided plunger 11 by means of the follower pin 19 which engages the placement angle guide slot 11a of the plunger. Since the latter is a part of the rigid head carrier assembly (parts 3, 3a, 3b, 11 and 12), its motion constitutes the primary displacement component X of the dressing head 2 along the contour of the grinding disc 1. The upper eccentric drive crank 8, when adjusted for a given eccentricity in relation to the axis of shaft 7, simultaneously imparts a longitudinal motion to the guided upper plunger 10, whose rack teeth b then generate a rotationalmotion of angle B on the pinion 15..This motion is transmitted to the eccentric 16 by the secondary shaft 17. The rotational motion of the eccentric l6 in turn is transmitted over the fork 3b to the head carrier-assembly which executes a rocking motion of angle -y and .accordingly raises and lowers the dressing head 2 in the secondary direction Y. The sum of the two motion components X and Y produces the desired convexly corrected displacement path of the dressing head 2 along the outline of the grinding wheel 1.

The total dressing stroke in the primary direction X is adjustable through adjustment of the eccentricity of the follower pin 90 on the crank 9, the length of the stroke being indicated by the pointer 13 and dial 14. The desired convexity of the grinding wheel outline in the secondary direction Y can be adjusted on the eccentric crank 8, through adjustment of the follower pin 80. The result of this adjustment is visible as a reading on the scale 21 against the stationary pointer 20. If the follower pin 8c is positioned in alignment with the shaft 7, as is shown in the drawing, the angular motion of eccentric 16 is ,8 O, in which case the dressing head 2 executes a straight-line motion on the grinding wheel 1.

During adjustment of a curved displacement path of the dressing head 2, when it is found that a straight line connecting the end points of the motion path is not parallel to the straight line of the theoretical taper, adjustment can be made of the angular position of the eccentric 16 in relation to the pinion to correct the skew of the path curvature. For this purpose, the clamping screw 18 is released, and an angular adjustment, readable at the dial 22 against pointer 19a, is made between the eccentric l6 and pinion 15.

It should be understood, of course, that the foregoing disclosure describes only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of this example of the invention which fall within the scope of the appended claims.

I claim:

1. In a grinding wheel dressing device adapted for the dressing of gear cutter grinding wheels, especially grinding wheels for helically fluted envolute gear cutters, a mechanism for generating an adjustable dressing point motion along a dressing arc of infinitely variable chord length and independently infinitely variable are height, the mechanism comprising in combination:

motion generating means for executing a repeating motion of constant motion length; first motion translating means connected to said motion generating means for deriving from its repeating motion a primary straight-line reciprocating motion, siad first motion translating means including means for adjusting the length of said primary reciprocating motion; second translating means connected to said motion generating means for deriving from its repeating motion a secondary reciprocating motion, said second motion translating means including means for adjusting -,the length of said secondary reciprocating motion between a maximum length and zero length, independently of the adjusted length of said primary reciprocating motion;

a grinding wheel dressing head having a dressing point attached thereto, the dressing head being movable for dressing point displacements along 2 of freedom which-are substantially perpendicular to one another;

means for directly transmitting said primary reciprocating motion to the dressing head as a primary dressing point motion of a length corresponding to the chord length of said dressing arc; and

means for simultaneously transmitting said secondary reciprocatingmotion to the dressing headfindep'endently of said primary reciprocating motion, as a secondary dressing point motion of a length corresponding to the dressing arc height;

said mechanism being thus capable of generating arcuate dressing point motions of infinitely variable "chord length and of infinitely variable are height, including straight-line motions of zero arc height.

2. A mechanism as defined in claim 1 wherein:

the second motion translating means further includes means for skewing the secondary reciprocating motion through unequal shifting of the motion reversal points in relation to said secondary motion transmitting means.

3. A mechanism as defined in claim 2, further comprising:

dial means for producing a reading indicative of the end points of the primary motion of the dressing point;

dial means for producing a reading indicative of the extent of the secondary motion of the dressing point; and

dial means for producing a reading indicative of the skew of said secondary motion.

4. A mechanism as defined in claim 2, wherein:

the motion generating means includes a first shaft and means for rotating said shaft between two preset angular positions;

the first motion translating means further includes an eccentric drive crank of adjustable eccentricity which is connected to the first shaft, and a guided reciprocating member cooperating with said drive crank; and

the second motion translating means further includes a similar eccentric drive crank of adjustable eccentricity connected to the first shaft, and a cooperating reciprocating member, the eccentricity of the crank being adjustable to zero, to permit optional elimination of the secondary reciprocating motion.

5. A mechanism as defined in claim 4, wherein:

the eccentric drive cranks of the first and second motion translating means include each:

a hub mounted on the first shaft;

a crank arm extending radially from the hub;

a follower pin at one end of the crank arm, the follower pin engaging said respective cooperating reciprocating member; and

means for clamping the crank arm to the hub at different radial distances of the follower pin.

6. A mechanism as defined in claim 4, wherein:

the means for rotating the first shaft includes a pinion on said first shaft and a longitudinally movable rack engaging said pinion.

7. A mechanism as defined in claim 4, wherein:

the primary motion transmitting means includes a head carrier assembly, said dressing head being attached to the latter;

the guided reciprocating member of the first translating means is a first plunger, the plunger being guided for longitudinal motion along its axis;

the head carrier assembly is connected to said first plunger so as to be axially retained thereby and moving in unison therewith, the longitudinal plunger motion thus constituting said primary dressing point motion;

the head carrier assembly is pivotable about the axis of said first plunger and includes a head arm extending radially with respect to the plunger axis, the dressing head being carried on the far end of said head arm, an angular motion of the head carrier assembly thus constituting said secondary dressing point motion.

8. A mechanism as defined in claim 7, wherein:

the first plunger is cylindrical in shape and is guided for rotational motion about its axis; and

the head carrier assembly is rigidly attached to said first plunger.

9. A mechanism as defined in claim 7, wherein:

the secondary motion transmitting means includes a second shaft;

the reciprocating member of the second translating means is connected to said second shaft so as to produce an angular reciprocation of the latter; and the secondary motion transmitting means further includes means for converting the angular reciprocation of the second shaft into an angular motion of the head carrier assembly. 10. A mechanism as defined in claim 9, wherein: the means for skewing the secondary reciprocating motion includes means for adjusting the angle at i which the reciprocating member of the second translating means is connected to the second shaft.

11. A mechanism as defined in claim 9, wherein:

the reciprocating member of the second motion translating means is a second plunger extending perpendicularly to said second shaft and having rack teeth engaging a pinion on said shaft;

the head carrier assembly includes a forked member extending a distance from its pivot axis;

the second shaft is arranged in parallel alignment with the first plunger; and

the converting means of said secondary motion transmitting means is an eccentric mounted on the second shaft and engaging said forked member.

12. A mechanism as recited in claim 11, wherein:

the means for skewing the secondary reciprocating motion includes means for clampingly adjusting the relative angular positions of said pinion and eccentric on the second shaft. 

1. In a grinding wheel dressing device adapted for the dressing of gear cutter grinding wheels, especially grinding wheels for helically fluted envolute gear cutters, a mechanism for generating an adjustable dressing point motion along a dressing arc of infinitely variable chord length and independently infinitely variable arc height, the mechanism comprising in combination: motion generating means for executing a repeating motion of constant motion length; first motion translating means connected to said motion generating means for deriving from its repeating motion a primary straight-line reciprocating motion, siad first motion translating means including means for adjusting the length of said primary reciprocating motion; second translating means connected to said motion generating means for deriving from its repeating motion a secondary reciprocating motion, said second motion translating means including means for adjusting the length of said secondary reciprocating motion between a maximum length and zero length, independently of the adjusted length of said primary reciprocating motion; a grinding wheel dressing head having a dressing point attached thereto, the dressing head being movable for dressing point displacements along 2* of freedom which are substantially perpendicular to one another; means for directly transmitting said primary reciprocating motion to the dressing head as a primary dressing point motion of a length corresponding to the chord length of said dressing arc; and means for simultaneously transmitting said secondary reciprocating motion to the dressing head, independently of said primary reciprocating motion, as a secondary dressing point motion of a length corresponding to the dressing arc height; said mechanism being thus capable of generating arcuate dressing point motions of infinitely variable chord length and of infinitely variable arc height, including straight-line motions of zero arc height.
 2. A mechanism as defined in claim 1 wherein: the second motion translating means further includes means for skewing the secondary reciprocating motion through unequal shifting of the motion reversal points in relation to said secondary motion transmitting means.
 3. A mechanism as defined in claim 2, further comprising: dial means for producing a reading indicative of the end points of the primary motion of the dressing point; dial means for producing a reading indicative of the extent of the secondary motion of the dressing point; and dial means for producing a reading indicative of the skew of said secondAry motion.
 4. A mechanism as defined in claim 2, wherein: the motion generating means includes a first shaft and means for rotating said shaft between two preset angular positions; the first motion translating means further includes an eccentric drive crank of adjustable eccentricity which is connected to the first shaft, and a guided reciprocating member cooperating with said drive crank; and the second motion translating means further includes a similar eccentric drive crank of adjustable eccentricity connected to the first shaft, and a cooperating reciprocating member, the eccentricity of the crank being adjustable to zero, to permit optional elimination of the secondary reciprocating motion.
 5. A mechanism as defined in claim 4, wherein: the eccentric drive cranks of the first and second motion translating means include each: a hub mounted on the first shaft; a crank arm extending radially from the hub; a follower pin at one end of the crank arm, the follower pin engaging said respective cooperating reciprocating member; and means for clamping the crank arm to the hub at different radial distances of the follower pin.
 6. A mechanism as defined in claim 4, wherein: the means for rotating the first shaft includes a pinion on said first shaft and a longitudinally movable rack engaging said pinion.
 7. A mechanism as defined in claim 4, wherein: the primary motion transmitting means includes a head carrier assembly, said dressing head being attached to the latter; the guided reciprocating member of the first translating means is a first plunger, the plunger being guided for longitudinal motion along its axis; the head carrier assembly is connected to said first plunger so as to be axially retained thereby and moving in unison therewith, the longitudinal plunger motion thus constituting said primary dressing point motion; the head carrier assembly is pivotable about the axis of said first plunger and includes a head arm extending radially with respect to the plunger axis, the dressing head being carried on the far end of said head arm, an angular motion of the head carrier assembly thus constituting said secondary dressing point motion.
 8. A mechanism as defined in claim 7, wherein: the first plunger is cylindrical in shape and is guided for rotational motion about its axis; and the head carrier assembly is rigidly attached to said first plunger.
 9. A mechanism as defined in claim 7, wherein: the secondary motion transmitting means includes a second shaft; the reciprocating member of the second translating means is connected to said second shaft so as to produce an angular reciprocation of the latter; and the secondary motion transmitting means further includes means for converting the angular reciprocation of the second shaft into an angular motion of the head carrier assembly.
 10. A mechanism as defined in claim 9, wherein: the means for skewing the secondary reciprocating motion includes means for adjusting the angle at which the reciprocating member of the second translating means is connected to the second shaft.
 11. A mechanism as defined in claim 9, wherein: the reciprocating member of the second motion translating means is a second plunger extending perpendicularly to said second shaft and having rack teeth engaging a pinion on said shaft; the head carrier assembly includes a forked member extending a distance from its pivot axis; the second shaft is arranged in parallel alignment with the first plunger; and the converting means of said secondary motion transmitting means is an eccentric mounted on the second shaft and engaging said forked member.
 12. A mechanism as recited in claim 11, wherein: the means for skewing the secondary reciprocating motion includes means for clampingly adjusting the relative angular positions of said pinion and eccentric on the second shaft. 